Experimental study on the degradation mechanism of LaCoO3-based symmetric supercapacitors

Novel Design of Perovskite-Structured Neodymium Cobalt Oxide Nanoparticle-Embedded Graphene Oxide Nanocomposites as Efficient Active Materials of Energy Storage Devices

In recent years, electrochemical supercapacitors are expected to represent the future of energy storage device technology. Specifically, the excellent electrochemical performance with long cycle life, high energy, and power density is considered an essential criterion for commercial applications. Herein, we constructed a novel composite of neodymium cobalt oxide-encapsulated graphene oxide nanocomposite (NCO/GO) via a simple and robust method for a symmetric supercapacitor (SSC) device. The prepared samples were securitized by X-ray diffraction, Fourier transform infrared spectroscopy, Raman, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and Brunauer-Emmett-Teller analysis. The as-synthesized NCO/GO is deposited on nickel foam (NF) and used as a supercapacitor electrode (NCO/GO/NF), which exhibits superior specific capacitance (Cs) of 1080.92 F g-1 at 1 A g-1 and fantastic cycling life with ∼89.42% retention after 10,000 cycles at 10 A g-1 in 1.0 M KOH aqueous electrolyte. A tremendous electrochemical performance of the hybrid nanocomposite electrode is obtained from the good redox activity and synergistic effects of the NCO spherical-like nanoparticles combined with the GO nanosheets. Furthermore, the assembled SSC device delivers significantly enhanced power density (932.93 Wh kg-1) and energy density (210.42 mWh kg-1). Moreover, the SSCs exhibit excellent cycling stability with ∼82.19% capacity retaining over 10,000 charge/discharge cycles. Remarkably, a 1.8 V red light-emitting diode (LED) can be lit up for more than 10 min by series connection SSCs. Thus, the obtained results indicated that the NCO/GO/NF//NCO/GO/NF symmetric device has a robust and cost-effective electrode material for high-performance supercapacitor systems.

Performance degradation study of NiCo2O4-based asymmetric supercapacitors

The performance of NiCo2O4//GO asymmetric supercapacitors was found to decline after many tests. It was found that the performance of the GO electrode was almost unchanged, while the performance of the NiCo2O4 electrode declined rapidly. Therefore, porous spherical NiCo2O4 nanoparticles were synthesized via a simple hydrothermal method. A NiCo2O4//GO asymmetric supercapacitor was made, which can be charged and discharged 3000 times in the current density of 10 A g-1. The surface morphology, crystal structure and elemental composition were characterized by X-ray diffraction analysis, scanning electron microscopy and X-ray photoelectron spectroscopy. By comparing the surface morphology, crystal structure and elemental composition of the NiCo2O4 electrode before and after the cycle, it was found that the performance of NiCo2O4 electrode declines rapidly after the cycle due to the formation of new substances and the destruction of the crystal structure of NiCo2O4 electrode. Therefore, maintaining the stability of the crystal structure of the electrode material is an important means to ensure the stability of the performance of the supercapacitor. It provides a meaningful strategy for studying the degradation of supercapacitor electrode materials.

Cycling stability of Fe2O3 nanosheets as supercapacitor sheet electrodes enhanced by MgFe2O4 nanoparticles

The Fe₂O₃ material is a common active material for supercapacitor electrodes and has received much attention due to its cheap and easy availability and high initial specific capacitance. In the present study, we prepared adhesive-free Fe₂O₃ sheet electrodes for supercapacitors by growing Fe₂O₃ material on nickel foam by hydrothermal method. The sheet electrode exhibited a high initial specific capacitance of 863 F g^-1, but we found that the sheet lost its specific capacitance too quickly through cyclic stability tests. To solve this problem, Fe₂O₃/MgFe₂O₄ composites were grown on nickel foam (NF). It was found through testing that the cycling stability of the sheet electrode gradually increased as the content of MgFe₂O₄ material increased. When the molar ratio of Fe₂O₃ to MgFe₂O₄ material was 1 : 1, the initial specific capacitance of the sheet electrode was 815 F g^-1 and the capacitance remained at 81.25% of the initial specific capacitance after 1000 cycles. The better cycling stability results from the more stable structure of the composite, the synergistic effect leading to better reversibility of the reaction.

High-performance asymmetric supercapacitor based on CdCO3/CdO/Co3O4 composite supported on Ni foam

A CdCO₃/CdO/Co₃O₄ composite has been prepared on nickel foam through a combined hydrothermal-annealing method. An asymmetric hybrid supercapacitor (SC) device was assembled with this composite as the positive electrode and activated carbon was the negative electrode. The SC exhibited a high specific capacitance of 84 F g⁻¹ @ 1 mA cm⁻², a maximum energy density of 26.3 W h kg⁻¹, and a power density of 2290 W kg⁻¹, along with a wide potential window of 1.5 V and long cycle life (92% after 6000 cycles). SCs assembled in series powered various light-emitting diodes and moved an electrical mini-motor.

This work presents for the first time a CdCO₃/CdO/Co₃O₄@nickel foam based supercapacitor with high both specific capacitance and energy density, a widespread potential window and a long cycle life.